The only content that cannot be downloaded is the TS2010 built-in routes and sessions themselves. If you want these, you will have to add the TS2010 .ja files (and serial number) to your TS12.
Other than 2010 built-in assets as noted by Shane, save the 2010 assets that you want to import as CDP's in in 2010 (save to flashdrive or disc), then start 2012 CMP and import the CDP's that you just saved. Be aware that some of the imported assets may require repairs after committing.
He doesn't have 2010 showing in his station stops, and I think he's assuming incorrectly that the KUIDs he can't find on the DLS are 2010 built ins, they're probably from 3rd party websites.
